1. Field of the Invention
The invention relates to a new sheet anode, specifically to the sheet anode based on modified zinc-aluminum alloys and zinc-air batteries containing the same.
2. Description of the Related Art
Zinc-air batteries include a zinc anode, a separator, electrolyte, and an air cathode. The most commonly used electrolyte is concentrated potassium hydroxide (KOH). The theoretical specific energy and theoretical cell voltage are 1085 Wh/kg and 1650 mV, respectively. Low operating power and short cycle life were two major problems for zinc-air batteries. Great efforts have been made worldwide to develop better air cathodes and zinc anodes.
The efforts of research on Zn anode focused on the enhancement of cell capacity and cycle life of pure Zn, which being mainly made into electrolytic powders then blended with suitable binders and compacted into porous plates before use. The specific surface area of an electrode is an important parameter. A porous Zn anode performs higher utilization efficiency and lower anodic passivation than does a rolled Zn sheet anode. As for the binder for Zn powders, it is very common to use a gelling agent during compaction to fabricate a porous Zn anode. Othman et al. studied a new gelling agent. They used KOH-treated agar thin layer to improve the interfacial contacts. Rolled zinc sheet had been used as the anode at early stage of development the zinc-air batteries. However it was given up due to the inherently severe passivation during discharge. In this invention, the difficulty of using rolled zinc sheet is overcome by using two-phase-structured zinc alloys, which also serve to increase cell voltage and cell capacity.